Title: A novel neuronal signaling pathway for ethanol behavioral responses in Drosophila. Project Summary Neural changes that drive inappropriate behavior in addiction are due in part to transcription factor-dependent changes in expression of genes that set the form and function of the brain. Knowledge of how drugs like ethanol affect transcription factor activity and discovery of genes regulated by specific transcription factors will improve our understanding of drug action and provide new approaches to potential treatments. Drosophila is a useful model for identifying the molecules and mechanisms of action for ethanol. Flies exhibit behaviors that model features of addiction including ethanol sensitivity, tolerance, preference, and reward. Conservation of genes and sophisticated genetics facilitate a rapid pace of discovery. Preclinical translational studies have helped bridge basic findings in flies with models of addiction in higher organisms. Transcription factors of the nuclear receptor family are candidate targets for ethanol. We focus on one member of this family, NR4a1 and its fly homolog Hr38, that belongs to a class that is regulated by expression level, not ligand binding. In rodents NR4a1 is increased following acute ethanol exposure and in protracted abstinence. In flies we showed that Hr38 expression is similarly increased in specific brain regions following acute ethanol exposure. Importantly, we provide evidence that mutation of Hr38 results in altered ethanol behaviors, implicating Hr38 and likely the genes that it regulates in the actions of ethanol. Our goal is to define the signaling pathway that ethanol uses to increase Hr38 expression and determine the consequences of perturbing pathway components. Published evidence points to two Hr38 signaling pathways that include molecules implicated in the actions of ethanol. Some of these molecules are also thought to be important for the effects of social environment, which in turn can have profound effects on alcohol consumption in humans and animal models. The expected outcome of the proposed studies will be a functional description of a novel signaling pathway engaged by ethanol. In future studies we plan to identify effector pathways that alter neuronal function.